The invention is a contact device and a process to facilitate contact of power electronics components as well as an assembly that consists of one or several power electronics components that are contacted with strip conductors on a carrier.
The current state of technology generally recognizes the following processes to facilitate contact of integrated electronic components (chips):
In the case of so-called Drahtbonden [wire bonding], a semiconductor component is placed onto a substrate, whereby fine gold or aluminum wires connect the components' metallic contact surfaces (bond pads) with the substrate's contacts. The fine gold or aluminum wires are fastened to the contact surfaces by means of ultrasound welding, for example. The serial nature of the contacting process makes wire bonding relatively time-intensive.
Therefore, industrial-scale production of microelectronic components also employs the so-called Tape Automated Bonding (TAB) method, whereby a copper comb, produced by means of etching on a plastic carrier (tape), is placed on the upper side of the component and simultaneously bonded by means of thermal compression with all contact surfaces on the component.
In addition, the so-called flip chip method is a common method whereby a chip is bonded directly with the substrate. Accordingly, so-called solder bumps are produced on the contact surfaces of the component's underside. When the entire substrate is warmed, these bumps become bonded with the substrate's strip conductors.
However, due to their small contact surfaces, for instance, these commonly-known methods of facilitating contact are not entirely suitable for applications where larger amounts of power will be transferred. While it is true that power electronics components, such as power MOSFETs, are generally bonded to a substrate's contacts by means of wire bonds, the high levels of current necessitate the use of several wires for each power contact (the source and drain of a MOSFET, for example). For this reason, the use of wire bonds to contact power electronics components is relatively time-consuming and expensive. Also, inductance of the bond wires can cause distortions of the signal at high frequencies.
In the past, power electronics components were generally not placed onto a substrate in an unencapsulated condition; instead, they were enclosed in a housing. For example, German patent DE-PS 19 11 633 reveals a method of contacting and enveloping semiconductor components whereby the component is assembled onto a stamped lead frame. Accordingly, the component, such as a high performance transistor (whose contact surfaces are covered with solder), is placed onto a plate-like portion of the lead frame and the ends of the lead frame's narrow lead bridges are placed onto the contact surfaces on the transistor's upper side. The frame and the component are then placed together into a pressing mold, the temperature is increased until the solder melts, and the press mold is later filled with a plastic material. Finally, parts of the lead frame, which protrude from the encapsulated component, are removed in order to electrically separate from each other the leads to the individual contacts.
U.S. Pat. No, 4,809,054 also demonstrates a method of contacting semiconductor elements with a lead frame. The contact surfaces arranged on the upper side and underside of the component are covered with solder, the component is placed onto a right-angle section of the lead frame, and another section of the lead frame is folded over in such a way that it contacts the contact surface on the upper side of the component.
German patent DE 199 33 975 is also mentioned. It describes a pressed screen for contacting the connections of an assembly that consists of several electronic parts.
The invention pursues the objective of providing a cost-effective system for contacting power electronics components with which mechanically and electrically stable and especially low-inductance connection paths to the component's contacts can nevertheless be created.
The invention achieves this objective by means of the methods and devices detailed in claims 1, 7, and 14. Preferred designs for executing the inventions are provided in the respectively subordinate claims, as well as other places.